Solar Storm Expected to Hit Earth Tuesday

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A medium-size solar flare erupted from the sun this weekend,
hurling a cloud of plasma and charged particles toward Earth on a
cosmic path that is expected to deliver a glancing blow to our
planet tomorrow (July 31), according to space weather
forecasters.

The M6-class solar flare exploded from the sun on Saturday (July
28), unleashing a wave of plasma and charged particles, called a
coronal mass ejection (CME), into space. The CME is expected
to reach Earth tomorrow, and could deliver a glancing blow to
Earth's magnetic field at around 11 a.m. EDT (1500 GMT),
according to the website Spaceweather.com, which regularly
monitors space weather events.

"This is a slow-moving CME," astronomer Tony Phillips wrote on
Spaceweather.com. "The
cloud's low speed (382 km/s estimated) combined with its glancing
trajectory suggests a weak impact is in the offing. Nevertheless,
polar geomagnetic storms are possible when the cloud arrives."

Powerful, fast-moving CMEs that hit Earth directly can trigger
strong geomagnetic storms that cause radio blackouts and disrupt
power grids and other communications infrastructure. These clouds
of charged particles can also knock out satellites as they travel
through space.

A more benign effect of solar storms, however, is supercharged
northern and southern lights, which can be sparked when the
CME's charged particles hit Earth's magnetic field. Solar storm
forecasts are often accompanied by alerts for auroras at high-
and mid-latitudes, though particularly strong geomagnetic storms
can generate auroras at lower-than-normal latitudes.

"The CME will also hit Mercury, probably with greater force,"
Phillips wrote on Spaceweather.com. "Mercury's planetary magnetic
field is only ~10 percent as strong as Earth's, so Mercury is not
well protected from CMEs. When the clouds hit, they can actually
scour atoms off Mercury's surface, adding material to Mercury's
super-thin atmosphere and comet-like tail."

The sun's activity waxes and wanes on a roughly 11-year cycle.
The sun's current cycle, called Solar Cycle 24, began in 2008.
The sun's activity is expected to ramp up toward a solar maximum
in 2013.

Editor's note: If you snap aurora or sunspot photos that you'd
like to be considered for use in a story or gallery, please send
them to SPACE.com managing editor Tariq Malik at tmalik@space.com.